In a substrate processing apparatus such as a plasma ashing apparatus or a CVD (Chemical Vapor Deposition) apparatus for performing a required process on a substrate, e.g., a semiconductor substrate, a flat panel display substrate, or the like, there is known that when a vacuum processing chamber is evacuated to vacuum after maintenance accompanied by opening to the atmosphere, particle contamination is caused by, e.g., dispersion of particles.
The attachment of particles onto parts included in the chamber contaminates a substrate (hereinafter, referred to as “wafer”) in subsequent processes or makes it difficult for the wafer to be adsorbed on a surface of a mounting table. This may cause a process failure or abnormal discharge.
If the interior of the chamber is evacuated while a wafer is mounted on the mounting table (hereinafter, referred to as “stage”) and if mapping measurement is made after evacuation for particles attached on a surface of the wafer, a particle map is often observed which duplicates the array of gas holes of a shower head disposed to face the stage. From the above observation, it can be seen that, during evacuation, particles are dispersed from the gas holes of the shower head and attached onto the stage. Such particles in the chamber may be originated from particles entered from the external environment into the chamber during maintenance, particles remaining in a gas line, particles generated by condensation of moisture, and the like.
Furthermore, it is known that gases are released or outgassed from parts included in the chamber during evacuation. The out-gases do not only prolong an evacuation time needed to lower the inner pressure of the chamber down to a required vacuum level, but also cause problems such as process variation, abnormal discharge, or the like. The term “out-gases” used herein refers to gases released or outgassed from parts inside the processing chamber during vacuum evacuating thereof.
FIG. 13 illustrates a relationship between an amount of a species in out-gases generated from parts included in a chamber of a substrate processing apparatus and a release time thereof.
It can be seen from FIG. 13 that the species in the out-gases may include N2/CO, O2, and CO2 in addition to moisture (H2O), which have been entered from the external environment when the chamber was opened to the atmosphere. It can also be seen that the amount of released moisture is greater by at least one order of magnitude than the amount of the other released species, and thus main species of the out-gases is moisture. An alumite based material, thermally sprayed yttria based material, ceramics based material, carbon based material, or the like may be considered as a material that releases a great amount of out-gases.
There is known a technology of reducing particles generated in the chamber of the substrate processing apparatus during chamber evacuation (see, e.g., Japanese Patent Laid-open Application No. 1996-255784). The patent application supra discloses a vacuum processing method for use in an apparatus provided with a wafer stage for mounting thereon a wafer at a bottom portion of a vacuum processing chamber; a wafer stage cover for vacuum-sealing the interior of the vacuum processing chamber; a gas inlet line for introducing a gas into the sealed vacuum processing chamber that is formed by the wafer stage and the wafer stage cover; and a vacuum exhaust line for performing evacuation. In the vacuum processing method, the gas is injected from the gas inlet line to the wafer mounted on the wafer stage to blow particles off the wafer and then the particles are sucked through the vacuum exhaust line.
In the above prior art, the gas is injected toward the wafer to blow particles off the wafer, and then the particles are exhausted through the vacuum exhaust line. However, the blown particles may be attached to and remain on other parts included in the chamber so that particles may not be removed completely. Therefore, there is a need for a technology that can effectively collect particles present in the chamber and introduced into the chamber during evacuation, and adsorb out-gases generated during evacuation to remove the particles and the out-gases.